Effects of a defective lambda sensor

If the sensor is fatigued, its signal may be too weak or too slow. In addition to normal ageing, other defects can also occur. Here the respective damage patterns provide insight into the cause of the fault.

If the engine control unit does not receive the signal of the lambda sensor or the signal is too weak, it is in a sort of "blind flight". It cannot determine how the currently combusted mixture is composed. As a result, it switches to emergency mode and automatically runs a rich mixture. In other words: It adds more fuel than would be necessary. In doing so, it guarantees the sought-after performances and protects components from overheating.

This has negative consequences: On the one hand, the vehicle's consumption increases noticeably - by up to 15 % on average, and considerably more for city driving. In addition, the catalytic converter can no longer work properly and more harmful emissions are released to the environment.